title: Magnesium modulates parathyroid hormone secretion and upregulates parathyroid receptor expression at moderately low calcium concentration.
abstract: BACKGROUND
  The interest on magnesium (Mg) has grown since clinical studies have shown the efficacy of Mg-containing phosphate binders. However, some concern has arisen for the potential effect of increased serum Mg on parathyroid hormone (PTH) secretion. Our objective was to evaluate the direct effect of Mg in the regulation of the parathyroid function; specifically, PTH secretion and the expression of parathyroid cell receptors: CaR, the vitamin D receptor (VDR) and FGFR1/Klotho.
  
  
  METHODS
  The work was performed in vitro by incubating intact rat parathyroid glands in different calcium (Ca) and Mg concentrations.
  
  
  RESULTS
  Increasing Mg concentrations from 0.5 to 2 mM produced a left shift of PTH-Ca curves. With Mg 5 mM, the secretory response was practically abolished. Mg was able to reduce PTH only if parathyroid glands were exposed to moderately low Ca concentrations; with normal-high Ca concentrations, the effect of Mg on PTH inhibition was minor or absent. After 6-h incubation at a Ca concentration of 1.0 mM, the expression of parathyroid CaR, VDR, FGFR1 and Klotho (at mRNA and protein levels) was increased with a Mg concentration of 2.0 when compared with 0.5 mM.
  
  
  CONCLUSIONS
  Mg reduces PTH secretion mainly when a moderate low calcium concentration is present; Mg also modulates parathyroid glands function through upregulation of the key cellular receptors CaR, VDR and FGF23/Klotho system.
authors.affiliation: Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC), Reina Sofia University Hospital/University of Cordoba, Spain.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Rodríguez-Ortiz
authors.forename: Antonio
authors.initials: A
authors.lastname: Canalejo
authors.forename: Carmen
authors.initials: C
authors.lastname: Herencia
authors.forename: Julio M
authors.initials: JM
authors.lastname: Martínez-Moreno
authors.forename: Alan
authors.initials: A
authors.lastname: Peralta-Ramírez
authors.forename: Pablo
authors.initials: P
authors.lastname: Perez-Martinez
authors.forename: Juan F
authors.initials: JF
authors.lastname: Navarro-González
authors.forename: Mariano
authors.initials: M
authors.lastname: Rodríguez
authors.forename: Mirjam
authors.initials: M
authors.lastname: Peter
authors.forename: Kristina
authors.initials: K
authors.lastname: Gundlach
authors.forename: Sonja
authors.initials: S
authors.lastname: Steppan
authors.forename: Jutta
authors.initials: J
authors.lastname: Passlick-Deetjen
authors.forename: Juan R
authors.initials: JR
authors.lastname: Muñoz-Castañeda
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Almaden
mesh_terms: D000818:Animals; D002118:Calcium / Q000097:blood / Q000494:pharmacology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D015870:Gene Expression; D007150:Immunohistochemistry; D017616:Magnesium Compounds / Q000494:pharmacology*; D010280:Parathyroid Glands / Q000187:drug effects* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000235:genetics / Q000378:metabolism; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000235:genetics / Q000378:metabolism*; D018167:Receptors, Calcitriol / Q000235:genetics / Q000378:metabolism; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D017616:Magnesium Compounds; D010281:Parathyroid Hormone; D010710:Phosphates; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1; D018167:Receptors, Calcitriol; D044169:Receptors, Calcium-Sensing; C030781:magnesium phosphate; C496350:Fgfr1 protein, rat; D051496:Receptor, Fibroblast Growth Factor, Type 1; D002118:Calcium
keywords: PTH; calcium-sensing receptor; magnesium; parathyroid glands; vitamin D receptor